In a nuclear power plant or thermoelectric power plant, uranium, petroleum, coal, or the like is used as fuel to generate heat, and the generated heat is used to heat water circulating through a system and generate steam. The generated steam rotates a turbine, thus producing electricity. The steam that has passed through the turbine is cooled by a condenser and changed to water again. Particularly, in a steam circulation power generation method, a water-cooling condensation process using water requires a large amount of cooling water. Given this, seawater is used as cooling water to be used in the condenser. Therefore, to smoothly supply seawater to be used as cooling water and discharge the used seawater, a power plant using the steam circulation power generation method is generally installed near the shore.
The condenser, which is a container provided to return steam to water again, is configured such that seawater continuously flows through a heat transfer tube of the condenser so as to continuously reduce the temperature of an inner wall of the condenser. Then, steam, which has come out of a valve and thus been used to rotate the turbine, directly collides with the inner wall of the condenser and, simultaneously, is cooled and condensed, thus returning to water. The condensed water returns to a boiler pipe again and then is heated to form steam of approximately 500° C. The heated steam is supplied to the turbine through the valve again.
In the boiler, hot water is changed to supersaturated steam, and the steam is discharged to the turbine through the valve. In the condenser, the steam is rapidly cooled and returned to water. This process is continuously repeated.
Here, to cool the outer wall of the condenser, much larger amount of cooling water than the amount of cooling water required to cool typical mechanical frictional heat is needed. Hence, while a power generator is operated, seawater must be continuously supplied.
With regard to the condenser, steam which has been used to rotate the turbine comes into contact with the inner wall of the condenser, and thus is cooled and returned to water. To increase the amount of steam coming into contact with the inner wall of the condenser, the condenser is formed of a plurality of heat transfer tubes so as to increase a contact area.
The condenser is problematic in that the outer surfaces of the heat transfer tubes may be corroded by condensation, or corrosion or the like of the heat transfer tubes may be caused by condensed fluid remaining on the surfaces.
In an effort to overcome the foregoing problems, a method of coating a heat transfer tube with fluoroplastic was proposed in Korean Patent Unexamined Publication No. 10-2000-0074647. This method includes an operation of simply spraying coating solution onto the surface of the heat transfer, and a sintering operation. However, several thousands of heat transfer tubes are needed in a condenser. Hence, if the several thousands of heat transfer tubes are coated by a simple spray method, the outer surfaces of the heat transfer tubes cannot be uniformly coated. There was proposed another coating method, in which heat transfer tubes are manufactured into a cylindrical bundle, and the cylindrical bundle is immersed in coating solution. However, because the cylindrical bundle floats due to buoyancy during the immersion operation, it is not easy to perform the coating process. In addition, coating solution may enter even the internal space of the heat transfer tubes. Furthermore, if the cylindrical bundle is assembled after the heat transfer tubes are coated one by one, there are problems in that a manufacturing process is complex, and the outer surfaces of the heat transfer tubes may be damaged. In the case of the conventional art, heat transfer tubes are coated one by one and then assembled into a cylindrical bundle. However, the conventional art has serious problems in that a coating process and a bundle assembly process are complex, and the surfaces of the heat transfer tubes may be damaged during the assembly process.
Therefore, it is urgent to develop a coating system capable of efficiently and uniformly coating the heat transfer tubes of the condenser.